The Genera Cetrariastrum and Concamerella (Parmeliaceae): A Chemosystematic Synopsis

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Abstract
The pantropical genus Cetrariastrum ( = Everniastrum Hale) has its center of diversity in the highlands of northern South America and of Mesoamerica but it also occurs in the mountains of southern Africa and southern Asia. It was probably differentiated in Gondwanaland, but tropical-island disjunctions reveal the efficacy of long-distance dispersal for a few of its commonest species. Two species earlier thought to belong to it but endemic to a xeric region of southeastern South America differ in having exceptionally thick upper cortices riddled with special algae-containing chambers, an apparent adaptation to their harsh habitat. They form the new genus Concamerella. Both Cetrariastrum and Concamerella have secondary-product chemistries characterized by β-orcinol depsidones and fatty acids. Excluding the fatty acids, 17 known compounds are reported from the former and seven from the latter, based upon the thin-layer chromatographic analyses of 415 specimens. Three species earlier included in Everniastrum are assigned to Parmotrema or Hypotrachyna. Cetrariastrum consists of 23 species; 22 of these comprise four that are new, six that are validations of older names and 12 that are new combinations.